I am at a total loss. I used ASTAP plate solving all along with great results. This new options menu is completely confusing and no matter what options I choose nothing . Plate solving does not work. I would like to have the one button push here solution where we could just select our preferred solver. What are the correct option selections to get ASTAP to work again? We need to keep this simple.... Bruce

You can change the solving method to Local ASTAP from the Alignment options window. That should get you back to what you were using before.
That being said, it is worthwhile getting the new Internal Solver working, as it is very fast. And to do so is most likely simply a matter of installing your required intex files.

Sorry tried that, no dice.
I was able to get a plate solve using astronomy.net but that is unacceptable. I want fast and accurate which I had with ASTAP. I am looking for one button which I used to have. Let me make the choice when the new solver works. As it stands no option I chose would work with the new solver or astap. IF I can not make it work with one button it is a step backward. Just choosing ASTAP local did not work. There are an infinite number of choices now. I just want simple and 100% reliable. How do I choose which extraction method?? There is no explanation for what that is, so I had to guess and tried them all. Which Options profile, again no explanation so how do I choose. Just give us back the old interface, if necessary the options button for advanced selection of new options. or methods. I will select the one that works all the time and is fast.

I spent about 40 minutes last night getting plate solving to work again for me. Like you, I had previously been successful at using ASTAP. After double-checking the Image Height value in the ASTAP settings and then playing with nearly every permutation of all those choices on the StellarSolver Options menu, I finally noticed that the FOV field in the main Align tab had some nonsensical value. I put the correct FOV there and the internal solver started working (and it is *very* fast!). I should check ASTAP next time out, as it may be that setting the FOV directly in ASTAP no longer matters.

Yes, key is that the FOV is set correctly and that the pixel scale matches what the Solver expects. If the pixel scale is off by too much, the solver will fail.
I only once had the problems describe here, and at that time the FOV was incorrect. Changing that immediately yielded superb results.
I use Stellar Solver at the Default setting (1) and I keep just the minimum number of index files in the folder I specify for the Solver to search for them. The fewer index files, the less needs to be loaded into memory, and the faster the solve.
Generally, solving now takes just around 1 s, sometimes a little less even. Just use internal solver, internal sep and default profile.
Jo

Also be sure the gain is turned up high enough if you're trying to plate solve in the simulator. Mine consistently failed under 50. Was driving myself crazy trying to figure this out. Higher gain = more stars = easier solves.

Now that this works, holy guacamole, somebody give Rob Lancaster a medal. I don't know if jubilant cursing is allowed on this forum but mother@$#&er this thing is %*#$ing brilliant.

Thankyou for your replies. I have used Stellarmate for ever since the RPI4 came out. So I am very familiar with how the plate solve works. This appears to be a driver issue for the RST 400 mount.